1. Field of the Invention
This invention relates generally to containers of various kinds which contain flowable material under pressure and are adapted to be dispensed when a valve is operated and relates particularly to a container having a concave or inwardly extending surface at both ends of a generally cylindrical body as well as to the method of filling the container with flowable material in a manner to substantially exclude air from the container when the top is placed thereon.
2. Description of the Prior Art
Heretofore pressurized dispensing containers have normally been separated into three groups. The first group includes aerosol containers in which the product to be dispensed is usually mixed with a fluorocarbon material having a low boiling point so that when the valve is opened the product and the carrier are both dispensed from the container. The second group of product dispensing containers has included a piston located within the container with the product to be dispensed on one side of the piston and a gas under pressure on the opposite side of the piston in a sealed chamber. The gas under pressure normally is air and when the valve is opened, the pressure on the product is relieved and the gas forces the piston against the lower portion of the product to cause the product to be discharged through the valve. The third group of containers for dispensing material under pressure includes containers having a flexible collapsible bag in which the material to be dispensed is located and fluid under pressure substantially completely surrounds the bag so that when the valve is opened the bag is collapsed by the fluid under pressure and the material within the bag is forced outwardly through the nozzle.
The present invention is concerned only with the type of dispenser having a generally cylindrical body with a piston movably mounted therein. This type of container normally requires that substantially all of the air be excluded therefrom before the container is used, otherwise a pocket of air collects adjacent to the valve and when the valve is opened the first time the discharge of air expels a small quantity of product at a high velocity and causes the product to spatter over a wide area.
Some representative art of piston type dispensing containers are the patents to Kaye et al. U.S. Pat. No. 2,809,774; Mahon et al. U.S. Pat. No. 2,895,650; Hoffman U.S. Pat. No. 3,022,923; Hein U.S. Pat. No. 3,099,370; Katz et al. U.S. Pat. No. 3,272,387; Towns U.S. Pat. No. 3,381,863; Knight et al. U.S. Pat. No. 3,415,425; Schultz U.S. Pat. Nos. 3,827,607 and 3,901,416; and Scheindel U.S. Pat. No. 3,897,672.